Polymers having vinyl aromatic block or having conjugated diene block and vinyl aromatic block, such as polystyrene, or triblock or five-block copolymer of styrene-butadiene or styrene-isoprene, have been commercialized as adhesive, sole, polymer modifier, etc. However, since the polymer of conjugated diene or vinyl aromatic monomer contains lots of unsaturated double bonds, its structure is highly unstable and tends to oxidize under heat or exposure to ultra violet or decomposition under other malign environments. Therefore, in order to improve the structural stability, such polymers are saturated by means of hydrogenation techniques.
There are lots of patents disclosing the hydrogenation catalyst system for such polymers. Of the related technical publications, U.S. Pat. No. 5,700,878 discloses a hydrogenation process in presence of a metal catalyst (such as Pt/Rh) on a silica support, wherein the silica support has a pore diameter greater than 600 angstroms, U.S. Pat. No. 6,376,622 discloses a hydrogenation process utilizing a metal catalyst, such as Pt/Rh. U.S. Pat. No. 6,841,626 discloses a hydrogenation process in presence of a metal catalyst (such as transition metal of VIII group from the periodic table) on an alumina support, wherein the alumina support has a pore diameter greater than 1,000 angstroms. U.S. Pat. No. 7,053,156 discloses a hydrogenation process in presence of Ni metal on an alumina support, wherein the alumina support has a pore diameter greater than 100 angstroms, U.S. Pat. No. 7,265,184 discloses a hydrogenation process in presence of a metal catalyst (such as metal of Ia, Ib, IIb, VIIb, VIIb, or VIII group from the periodic table) on a calcium silicate support, wherein the calcium silicate support has a surface area larger than 30 m2/g; U.S. Pat. No. 7,355,084 discloses a hydrogenation process in presence of Ru or Ru combined with transition metal of I, VII, or VIII group from the periodic table on a silicon oxide support.
Among all kinds of conventional hydrogenation processes, Pt as the catalyst has a superior effect on the hydrogenation of benzene ring, but Pt catalyst is very expensive. Therefore, there is a need to develop a catalyst system using cheaper metal.